Track pin with vented rubber plug

ABSTRACT

An improved method and apparatus are provided for sealing hollow pins which are commonly used as lubricant reservoirs in, e.g., track chain assemblies of crawler tractors, and linkage joints of earthmoving vehicles. One embodiment of the invention comprises a plug of elastomer material which has a lubricant passage axially therethrough, which passage receives an auxiliary plug means for the purpose of obturating the passage as well as causing radial expansion of the elastomer plug into positive engagement with a receiving axial bore in a hollow pin. The auxiliary expansion means takes the form of a screw, a spherical ball, or a headless plug employing a plurality of annular serrations. Another embodiment comprises a spherical ball which is received in a stepped, axial bore of a hollow pin and is retained therein by a Belleville washer. The invention facilitates refilling in the field of the lubricant reservoir contained within the pin.

United States Patent [191 Boggs et a1.

1 1 Oct. 2, 1973 1 1 TRACK PlN WlTll VENTED RUBBER PLUG [75] Inventors:Roger L. Boggs; David John Balzer,

both of East Peoria; Glenn Melvin Haslett, Peoria, all of 111.

[73] Assignee: Caterpillar Tractor Co., Peoria, 111.

[22] Filed: Apr. 2, 1971 [21] Appl. No.: 130,664

[52] US. Cl 305/14, 74/257, 138/89, 220/245, 220/DlG. 19, 305/59,308/120 [51] lnt. C1 862d 55/20 [58] Field of Search 220/245, DIG. 19;305/14, 59; 184/15 R; 74/257; 308/120; 138/89 OTHER PUBLICATIONS GermanPrinted App. No. 1, 955,005, Bruno, May

Primary Examiner-Richard J. Johnson Attorney-Fryer, Tjensvold, Feix,Phillips & Lempio [57] ABSTRACT An improved method and apparatus areprovided for sealing hollow pins which are commonly used as lubricantreservoirs in, e.g., track chain assemblies of crawler tractors, andlinkage joints of earthmoving vehicles. One embodiment of the inventioncomprises a plug of elastomer material which has a lubricant passageaxially therethrough, which passage receives an auxiliary plug means forthe purpose of obturating the passage as well as causing radialexpansion of the clastomer plug into positive engagement with areceiving axial bore in a hollow pin. The auxiliary expansion meanstakes the form of a screw, a spherical ball, or a headless plugemploying a plurality of annular serrations. Another embodimentcomprises a spherical ball which is received in a stepped, axial bore ofa hollow pin and is retained therein by a Belleville washer. Theinvention facilitates refilling in the field of the lubricant reservoircontained within the pin.

9 Claims, 8 Drawing Figures PATENTEDUCI ems 3.762'778 sum 1 [1F 2INVENTORS ROGER L. 80665 DAVID J. BALZER GLENN M. HASLETT i" T'TzlrPATENTEuum 2mm 3.762.778

sum 2 or 2 INVENTORS ROGER L. 80668 DAVID J. BALZER GLENN M. HASLETT f'2 :5 1/ %76 T'IORNEYS TRACK PIN WITH VENTED RUBBER PLUG BACKGROUND OFTHE INVENTION It is generally known that earthmoving equipment issubject to some of the most severe operating environ-.

ments demanded of any machines in everyday use. In particular, the trackchain assemblies of crawler tractors operate in intimate contact with anabrasive soil environment. The pin and bushing hinge joints which areused to articulately couple pairs'of spaced links that carryground-engaging track shoes are subject to extreme wear from abrasivematerial and very high stresses caused by engagement with drivesprockets.

Attempts have been made to increase service life of such trackassemblies by improved metallurgy, factory sealing and lubricating thejoints, and providing such factory-assembled joints in readily-serviced,plug-in cartridge form. Two forms of such sealed and lubricated hingejoints, disclosed in U.S. Pat. Nos. 3,463,560, and 3,492,054, haveproved effective in obtaining increased component life; however,production costs, which must be held to a minimum to assure customeracceptance through maximum product value, have proved to be a problem.

One problem related to cost reduction is effective and economicalsealing of the pin bores used for storing lubricant so vital forimproved internal wear of the joints. High manufacturing and servicecosts resulting from precision machining and machine downtime haveprecluded use of threaded and pressed-in steel plugs in the vastquantities of such lubricated hinge pins used by Another object is theprovision of auxiliary plug that serves both as a'vent closure andexpansion means that is capable of increasing unit loading of the plug'speripheral surface to obtain a maximum holding force whether it be usedfor a bore disposed axially in a pin or radially in the wall of atubular bushing.

Still another object is the ready accessibility and facility to removesaid expansion means for expedient represent-day industry. Materialcost, time and trouble of removing worn and corroded plugs for trackservice would be prohibitive and impractical. Alternate plugs, easier toinstall and service, and made of more economical elastomer material, areapplicable because they eliminate the basic problems of metallic plugswhich occur due to distortion from heat treatment, permanent seizure ofsuch plugs, and even minute scratches on the plugs, etc., thatcouldresult in the loss of SUMMARY AND OBJECTS OF THE INVENTION Inaccordance with the present invention, a simple and advantageous meanshas been found to expedite assembly and service of lubricated hingejoints by effectively employing a low-costelastomer plug for containinglubricant in a reservoir-type hinge pin.

A further advantage is the supplemental means of increasing thefrictional holding capability of the plug which also makes possibleexpedient replenishing of pin lubricant without physical removal of theplug.

It is therefore the object of the present invention to provideeconomical and efiective means of plugging reservoir pins employed insealed and lubricated hinge joints.

An additional object is to afford effective venting means for thereservoir regardless of how. supplemental fluid is added.

plenishing of the lubricant supply.

Still another object is the provision of an enhanced spherical plugwhich is removably retained in its operative environment by Bellevilleretaining means.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. lis a plan view in partial crosssection ofa hinge joint and a portion ofa track chain;

FIG. .2 shows a sectional view of a cartridge-type hinge joint; I

FIG. 3 is an enlarged cross-sectional view of a reservoir-type pin witha vent-type elastomer plug and assembled complementing auxiliaryexpansion plug;

FIG. 4 discloses another spherical-type auxiliary expansion plug;

FIG. 5 is a similar elastomer plug with a headless auxiliary expansionplug;

FIG. 6 is an alternate embodiment-ofthe elastomer plug in spherical formwith modified retaining means;

FIG. 7 is a plan view in section of a similar hinge joint wherein thebushing rather than the pin has an internal lubricant reservoir; I

FIG. 8 illustrates the method by which such hinge joints of wrapped andstored track would be filled with lubricating oil.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, thetrack assembly illustrated in FIG. 1 comprises a plurality of groundengaging track shoes 10 each of which are rigidly secured to a pair ofspaced, parallel, interconnected track links 12 as by a plurality ofbolts 14. Each pair of track links 12 is pivotally connected by means ofa hollow track pin 16 and a complementing coaxially disposed bushing 18to an adjacent and cooperating pair of links in such a manner that anarticulated track chain is formed. With all track sections coupled bysuch pin and bushing hinge joints an endless track chain is formed whichis trained over a drive sprocket and an idler sprocket disposed onopposite sides of a tractor (not shown) to afi'ord motivating andsteering means for an effective, crawler-type vehicle. Tracks of thepresent type are typically provided two-piece master track links (notshown) to facilitate assembly and service proce dures.

Pin 16 conveniently contains a central cavity 20 that is defined byclosed end 22 and or inlet open end 24 which makes possible areservoir-to contain a supply of lubricant. The lubricating fluiddistributed through radial bores 26 to the highly-loaded, coacting,intemallydisposed surfaces 28 of the pin and bushing contributessubstantially to extending the service life of these members. Suitableseals 30 are normally provided in the vicinity of the bushing ends tominimize loss of the viscous lubricating fluid and to prevent entry offoreign matter into the joints. As previously noted, suitable plug meanssuch as disclosed at 32 are necessarily provided to close the open endof hollow track pin 16 in order to retain the supply oflubricant storedwithin the reservoir in the track pin.

High-volume production and intricate assembly procedures of currentearthmoving tractors make use of threaded and/or tapered metallic plugsunfeasible because of the expense involved in their manufacture. Plugsmade of elastomer material which comprise this invention are a feasiblealternative to metallic plugs. However, to employ such plugssuccessfully, supplemental venting and retaining means in the form of anauxiliary plug means 34 is provided to obtain increased unit pressurefrom the resilient plug 32. Increasing the outward radial force byinternally positioned auxiliary plug means assures positive retention ofthe resilient plug under all environmental conditions including that ofincreased internal pressure that might occur in the reservoir duringoperations.

If excessive air or no air at all is provided in the reservoir, somefluid compartments can become highly pressurized during operations andconsequently starve critical components of vital lubricant. On otheroccasions, pressure can expel the sensitive plug seals, allowingdischarge of all oil from the reservoir. Air lock can also give faultyinitial readings resulting in insufficient lubricant to allow thecomponent to realize its anticipated service life.

As best shown in FIG. 3, elastomer plug 32 is preferably afforded atleast one small-diameter, full-length axial passage 36 which can beconveniently sealed by the screw-type auxiliary plug 34 after reservoirhas been filled. Passage 36 conventionally facilitates initial fillingof the lube reservoir 20 by readily receiving a thin hollow needlewhereupon hypodermic injection of the lubricant is accomplished whileair is vented out around the needle. 1

FIG. 2 discloses another type of sealed and lubricated joint in the formof a cartridge hinge joint 38 that has a hollow pin 40 with oneintegrally attached head 42 and a flanged, retainer cap 44 which isdetaehably secured by a screw 46 to a link member 48. This type of jointis typically employed in the bucket support linkage of end loaders, andcan incorporate at one end of the pin a similar resilient plug means 32having an auxiliary plug 34 to facilitate servicing of the joint.

Turning now to FIG. 3, there is shown in enlarged scale, how plug 32.may be inserted into open end 24 as shown at 32. The auxiliary passage36 can then receive supplemental fluid lubricant and be subsequentlysealed by a relatively coarse-threaded screw or auxiliary plug means 34.These threaded members may be formed of any suitable material includingplastic; however, it is desirable that the edges 50 of the threads 52 berounded because sharp edges can detrimentally affect theplug by adrilling or reaming action if the screw should be rotated excessively.Additionally, it is preferable that the root diameters of the screws bea minimum of one thirty-second of an inch larger than the vent passagein its swelled or compressed state. If a soft grade of rubber orelastomer is used for the resilient plug, a larger differential indiameters would be desirable.

FIG. 4 discloses still another auxiliary expansion plug 54 of aspherical shape that can be readily installed in the elastomer plugpassage 36 by any suitable impact tool that could be magnetized tofacilitate aligning and assembly of the minute ball plugs. Such a toolis as shown at 56 having a stepped end portion 58. To refill reservoir20, auxiliary ball plug 54 can be displaced by tool 56 such that it isexpelled from passage 36 into reservoir 20. The auxiliary ball plug 54may be made of plastic or metal and would be inexpensive enough to beconsidered disposable. After the reservoir is refilled in theconventional manner, a new auxiliary ball plug can be installed toobturate the passage.

In FIG. 5, there is shown a headless auxiliary plug 60 that employs aplurality of annular serrations 62 to effect increased outward radialholding force for the resilient plug and its positive retention in same.The advantage of this type plug is that it, like the aforementioned ballplug, may be simply forced on into the reservoir when refilling of thepin reservoir is required and a new pin can be inserted in its place. Insuch an operation, service time can be minimized and the member floatingabout in the reservoir can effectively keep residual compounds of thelube fluid from clogging the radial supply ports. Inexpensive plastic ormetal can similarly be used for these auxiliary plugs.

FIG. 6 discloses still another type of spherical reservoir plug 64 thatrequires a counterbored or stepped axial bore 66 for proper seating. Theinner surface of this elastomeric plug will sealingly abut acircumferential shoulder 68 and a close-fitting Belleville washerretainer 70 would be forcefully inserted in the bore and against theouter surface of the ball to keep the plug in place. The outwardexpansion of the conically-angled surface of the Belleville washerretainer maintains a one-way locking action. Conversely, snapping theretainer into an over-center condition by engaging and pulling it with athin hooked-end probe will allow removal of the washer and plug.

Turning to FIG. 7, there is represented a modified sealed and lubricatedhinge joint wherein a portion of the inner bore of the bushing ratherthan the pin is relieved to effect a fluid reservoir. In the event thepin plug is not readily accessible or a solid pin is required to affordmaximum joint strength, a similar elastomer plug means 72 can beemployed to close a radial port 74 in a reservoir bushing 76. The plugmay be obturated by auxiliary plug means 78. Preferably, the port wouldbe toward one end of the bushing to prevent the engagement of the drivesprocket from damaging the plug.

FIG. 8 illustrates a method by which a track chain using the inventionwould be conveniently filled with lubricating fluid as it is eitherwrapped or positioned on its side. Each pin bore would be quickly filledby hose from a central supply and closed with the vented plugs. All airtrapped beneath the plug is automatically expelled through the ventpassage by displacement as shown at during insertion of the plug.Installation of the auxiliary plug would then seal the vent passage.Introducing the oil into a pin bore already closed by a vented plugwould or could inherently exhaust most of the air in the upper part ofthe bore simply by placing the tractor on a hillside so that the plugsare in a vertically-elevated condition.

It is to be understood that the foregoing description is merelyillustrative of preferred embodiments of the invention and that thescope of the invention is not to be limited thereto, but is to bedetermined by the scope of the appended claims.

What is claimed is:

I. In a hinge joint comprising sealed and lubricated bearing meanscoupling at least two articulately jointed members, said bearing meansincluding a pin, a bushing disposed coaxially on said pin, and alubricant reservoir for supplying lubricant to the outer surface of saidpin, and wherein said lubricant reservoir has means defining an inletclosed by resilient plug means, and auxiliary plug means received inauxiliary means for receiving supplemental lubricant which comprises apassage through said resilient plug means, said passage beingdimensioned to receive the auxiliary plug means to both retain lubricantin the reservoir and to substantially increase surface unit loading ofthe resilient plug means by creating a high-level radially outwardlyacting expansive force within said resilient plug means so as to expandsaid resilient plug means into positive relation with said meansdefining an inlet.

2. The invention of claim 1 wherein the auxiliary plug means for saidresilient plug means passage comprises a spherical member of asufficient diameter to provide increased outward acting force from theresilient plug means to assure effective engagement of its peripheralsurface with the reservoir.

3. The invention of claim 1 in which said auxiliary plug means has asurface comprised of annular serrations.

4. The invention of claim 1 wherein said auxiliary plug means for saidresilient plug means passage is a threaded member capable ofself-engagement upon application of external force.

5. The invention of claim 4 in which the threads of said threaded memberhave round edges so as to be rotatable in said resilient plug without adestructive cutting action in the event it is rotated excessively.

6. The invention of claim 1 wherein said threaded member is made ofplastic.

7. In a chain link assembly comprising a first set of links, a bushingwith ends protruding through and secured to said links, a second set oflinks, a pin secured to the second set of links and mounted within thebushing for relative movement therewith, the pin having an open endlubricant reservoir therein with means communicating to the pin surface,the second set of links each having a recess coaxial with the pin withseal means disposed intermediate said links and the bushing ends,resilient plug means closing the open end of said reservoir, said plugmeans comprising passage means for receiving supplemental lubricant forthe pin and means for plugging said passage means, which latter meansact to increase surface unit loading of the resilient plug means toassure its retention under variable reservoir pressures.

8. In a hinge joint, the combination including a selfcontained, sealedand lubricated bearing assembly comprising a pin with an open-endlubricant reservoir therein with means communicating to the pin surface,a radially-enlarged head portion at one end of the pin and a flangemember affixed to the opposite spaced end of said pin, a relativelyrotatable bearing member supported on the pin intermediate andcontiguous to said pin head and flange, the inner surfaces of the pinhead and flange each containing an annular coaxial recess for receivingand maintaining seal means in an abutting relationship with said bearingmember, resilient plug means closing the open end of said reservoir,said plug means comprising auxiliary means for receiving supplementallubricant for the pin and means for plugging said auxiliary means whichlatter means acts to increase surface unit loading of the resilient plugmeans to assure its retention under variable reservoir pressures.

9. A hinge joint comprising sealed and lubricated bearing means couplingat least two articulately-joined members, said bearing means including apin and a bushing, disposed coaxially thereon, said bushing having aninside diameter larger than the pin, means communicating between theinside and outside bushing surfaces for introducing lubricating fluid tothe chamber effected between the oversized bushing and pin, resilientplug means closing said means communicating between the inside andoutside bushing surfaces, said plug means comprising auxiliary means forreceiving supplemental lubricant, and means plugging said auxiliarymeans, which latter means acts to increase surface unit loading of theresilient plug means so as to assure its retention under variablereservoir pressures.

1. In a hinge joint comprising sealed and lubricated bearing meanscoupling at least two articulately jointed members, said bearing meansincluding a pin, a bushing disposed coaxially on said pin, and alubricant reservoir for supplying lubricant to the outer surface of saidpin, and wherein said lubricant reservoir has means defining an inletclosed by resilient plug means, and auxiliary plug means received inauxiliary means for receiving supplemental lubricant which comprises apassage through said resilient plug means, said passage beingdimensioned to receive the auxiliary plug means to both retain lubricantin the reservoir and to substantially increase surface unit loading ofthe resilient plug means by creating a high-level radially outwardlyacting expansive force within said resilient plug means so as to expandsAid resilient plug means into positive relation with said meansdefining an inlet.
 2. The invention of claim 1 wherein the auxiliaryplug means for said resilient plug means passage comprises a sphericalmember of a sufficient diameter to provide increased outward actingforce from the resilient plug means to assure effective engagement ofits peripheral surface with the reservoir.
 3. The invention of claim 1in which said auxiliary plug means has a surface comprised of annularserrations.
 4. The invention of claim 1 wherein said auxiliary plugmeans for said resilient plug means passage is a threaded member capableof self-engagement upon application of external force.
 5. The inventionof claim 4 in which the threads of said threaded member have round edgesso as to be rotatable in said resilient plug without a destructivecutting action in the event it is rotated excessively.
 6. The inventionof claim 1 wherein said threaded member is made of plastic.
 7. In achain link assembly comprising a first set of links, a bushing with endsprotruding through and secured to said links, a second set of links, apin secured to the second set of links and mounted within the bushingfor relative movement therewith, the pin having an open-end lubricantreservoir therein with means communicating to the pin surface, thesecond set of links each having a recess coaxial with the pin with sealmeans disposed intermediate said links and the bushing ends, resilientplug means closing the open end of said reservoir, said plug meanscomprising passage means for receiving supplemental lubricant for thepin and means for plugging said passage means, which latter means act toincrease surface unit loading of the resilient plug means to assure itsretention under variable reservoir pressures.
 8. In a hinge joint, thecombination including a self-contained, sealed and lubricated bearingassembly comprising a pin with an open-end lubricant reservoir thereinwith means communicating to the pin surface, a radially-enlarged headportion at one end of the pin and a flange member affixed to theopposite spaced end of said pin, a relatively rotatable bearing membersupported on the pin intermediate and contiguous to said pin head andflange, the inner surfaces of the pin head and flange each containing anannular coaxial recess for receiving and maintaining seal means in anabutting relationship with said bearing member, resilient plug meansclosing the open end of said reservoir, said plug means comprisingauxiliary means for receiving supplemental lubricant for the pin andmeans for plugging said auxiliary means which latter means acts toincrease surface unit loading of the resilient plug means to assure itsretention under variable reservoir pressures.
 9. A hinge jointcomprising sealed and lubricated bearing means coupling at least twoarticulately-joined members, said bearing means including a pin and abushing, disposed coaxially thereon, said bushing having an insidediameter larger than the pin, means communicating between the inside andoutside bushing surfaces for introducing lubricating fluid to thechamber effected between the oversized bushing and pin, resilient plugmeans closing said means communicating between the inside and outsidebushing surfaces, said plug means comprising auxiliary means forreceiving supplemental lubricant, and means plugging said auxiliarymeans, which latter means acts to increase surface unit loading of theresilient plug means so as to assure its retention under variablereservoir pressures.